DNS REFERENCE

What is an SOA Record?

The administrative hub of the Domain Name System, declaring vital replication timers and contact information for a domain zone.

Understanding the Start of Authority (SOA) Record

An SOA Record (short for "Start of Authority") is a mandatory record that must exist at the very beginning of every DNS zone file. It marks the start of the zone and identifies the global administrative properties of the domain.

While records like A and MX deal with direct user routing, the SOA record is designed for communication between DNS servers. It tells secondary (backup) nameservers how frequently they should sync their databases with the primary master nameserver, how to handle sync failures, and who to contact in case of administrative problems.

A domain can have multiple NS records, but it must have **exactly one** SOA record.

Structure of an SOA Record

An SOA record contains a specific sequence of seven variables. Here is how they map inside a DNS query:

example.com. IN SOA ns1.dns-provider.com. hostmaster.example.com. (
  2026102401 ; Serial number (YYYYMMDDNN)
  7200        ; Refresh interval (2 hours)
  3600        ; Retry interval (1 hour)
  1209600     ; Expire limit (2 weeks)
  3600        ; Minimum TTL / Negative cache (1 hour)
)

Primary Nameserver (MNAME): The hostname of the master nameserver containing the original zone files.

Responsible Person (RNAME): The email address of the DNS administrator. Note that the "@" symbol is replaced by a dot (e.g. hostmaster.example.com).

Serial Number: A revision code. Whenever changes are made to the zone, this number increments. Secondary servers compare serials to check if they need to fetch zone updates.

Refresh Time: How long secondary nameservers wait before asking the master server if the zone has changed.

Retry Time: How long a secondary server waits before retrying a failed zone transfer from the master server.

Expire Time: The limit a secondary server can continue responding to queries if the primary master server remains offline. If reached, the zone data is discarded.

Minimum / Negative TTL: Tells recursive resolvers how long they should cache negative query responses (like NXDOMAIN - domain not found).

Query an SOA Record in Real Time

Enter a domain below to resolve and read its administrative SOA details:

KEY FACTS

Primary Use

Replicating zone files and caching negative lookup responses

Requirements

Exactly one record per DNS zone file

Output Value

Space-separated list of administrative parameters

OTHER DNS EXPLANATIONS

A Record →AAAA Record →CNAME Record →MX Record →TXT Record →NS Record →CAA Record →